ZyXEL Communications NXC2500 User Manual page 146

NAT and SNAT
NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address in a packet
in one network to a different IP address in another network. Use SNAT (Source NAT) to change the
source IP address in one network to a different IP address in another network.
Assured Forwarding (AF) PHB for DiffServ
Assured Forwarding (AF) behavior is defined in RFC 2597. The AF behavior group defines four AF
classes. Inside each class, packets are given a high, medium or low drop precedence. The drop
precedence determines the probability that routers in the network will drop packets when
congestion occurs. If congestion occurs between classes, the traffic in the higher class (smaller
numbered class) is generally given priority. Combining the classes and drop precedence produces
the following twelve DSCP encodings from AF11 through AF43. The decimal equivalent is listed in
brackets.
Table 71 Assured Forwarding (AF) Behavior Group
Low Drop Precedence
Medium Drop Precedence
High Drop Precedence
WMM
Wi-Fi Multimedia (WMM) provides basic Quality of Service (QoS) features to wireless networks. The
four categories of QoS described by WMM are: voice (VO), video (VI), best effort (BE), and
background (BK). These categories, known as a "access categories" (AC), are mapped to 802.1D
priority values which can then be mapped to their corresponding DSCP hex values.
Table 72 WMM to DiffServ Conversion on the NXC
Priority
Lowest
Highest
The WMM ACs as implemented on the NXC have the following functions:
VOICE: All wireless traffic to the SSID is tagged as voice data. This is recommended if an SSID is
used for activities like placing and receiving VoIP phone calls.
VIDEO: All wireless traffic to the SSID is tagged as video data. This is recommended for activities
like video conferencing.
Chapter 9 Policy and Static Routes
Class 1 Class 2
AF11 (10) AF21 (18)
AF12 (12) AF22 (20)
AF13 (14) AF23 (22)
WMM AC 802.1D Priority
BK 1
BK 2
BE 0
BE 3
VI 4
VI 5
VO 6
VO 7
NXC Series User's Guide
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Class 3 Class 4
AF31 (26) AF41 (34)
AF32 (28) AF42 (36)
AF33 (30) AF43 (38)
DSCP Hex Value
0x08
0x10
0x00
0x18
0x20
0x28
0x30
0x38